[U-Boot] [PATCH v2 04/13] drivers: serial: add driver for Microchip PIC32 UART controller.

[Purna Chandra Mandal <purna.mandal@microchip.com>]

Signed-off-by: Paul Thacker <paul.thacker@microchip.com>
Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>

---

Changes in v2:
- fix missing or corrupted chars during baud rate change
- remove loop until any new char is available in _getc()

 .../serial/microchip,pic32-uart.txt                |   5 +
 drivers/serial/Kconfig                             |  13 ++
 drivers/serial/Makefile                            |   1 +
 drivers/serial/serial_pic32.c                      | 230 +++++++++++++++++++++
 4 files changed, 249 insertions(+)
 create mode 100644 doc/device-tree-bindings/serial/microchip,pic32-uart.txt
 create mode 100644 drivers/serial/serial_pic32.c

diff --git a/doc/device-tree-bindings/serial/microchip,pic32-uart.txt b/doc/device-tree-bindings/serial/microchip,pic32-uart.txt
new file mode 100644
index 0000000..f00e215
--- /dev/null
+++ b/doc/device-tree-bindings/serial/microchip,pic32-uart.txt
@@ -0,0 +1,5 @@
+* Microchip PIC32 serial UART
+
+Required properties:
+- compatible: must be "microchip,pic32mzda-uart".
+- reg: exactly one register range.
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 1fc287e..9763ea1 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -107,6 +107,14 @@ config DEBUG_UART_APBUART
 	  will need to provide parameters to make this work. The driver will
 	  be available until the real driver model serial is running.
 
+config DEBUG_UART_PIC32
+	bool "Microchip PIC32"
+	help
+	  Select this to enable a debug UART using the serial_pic32 driver. You
+	  will need to provide parameters to make this work. The driver will
+	  be available until the real driver model serial is running.
+
+
 endchoice
 
 config DEBUG_UART_BASE
@@ -223,4 +231,9 @@ config UNIPHIER_SERIAL
 	  If you have a UniPhier based board and want to use the on-chip
 	  serial ports, say Y to this option. If unsure, say N.
 
+config PIC32_SERIAL
+	bool "Support for Microchip PIC32 on-chip UART"
+	help
+	  Support for the UART found on Microchip PIC32 SoC's.
+
 endmenu
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index dd87147..57cd38b 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_MXS_AUART) += mxs_auart.o
 obj-$(CONFIG_ARC_SERIAL) += serial_arc.o
 obj-$(CONFIG_UNIPHIER_SERIAL) += serial_uniphier.o
 obj-$(CONFIG_STM32_SERIAL) += serial_stm32.o
+obj-$(CONFIG_PIC32_SERIAL) += serial_pic32.o
 
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_USB_TTY) += usbtty.o
diff --git a/drivers/serial/serial_pic32.c b/drivers/serial/serial_pic32.c
new file mode 100644
index 0000000..3eddb57
--- /dev/null
+++ b/drivers/serial/serial_pic32.c
@@ -0,0 +1,230 @@
+/*
+ * (c) 2015 Paul Thacker <paul.thacker@microchip.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ *
+ */
+#include <common.h>
+#include <config.h>
+#include <dm.h>
+#include <clk.h>
+#include <serial.h>
+#include <wait_bit.h>
+#include <mach/pic32.h>
+#include <dt-bindings/clock/microchip,clock.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+/* UART Control Registers */
+#define U_MOD		0x00
+#define U_MODCLR	(U_MOD + _CLR_OFFSET)
+#define U_MODSET	(U_MOD + _SET_OFFSET)
+#define U_STA		0x10
+#define U_STACLR	(U_STA + _CLR_OFFSET)
+#define U_STASET	(U_STA + _SET_OFFSET)
+#define U_TXR		0x20
+#define U_RXR		0x30
+#define U_BRG		0x40
+
+/* U_MOD bits */
+#define UART_ENABLE		BIT(15)
+
+/* U_STA bits */
+#define UART_RX_ENABLE		BIT(12)
+#define UART_TX_BRK		BIT(11)
+#define UART_TX_ENABLE		BIT(10)
+#define UART_TX_FULL		BIT(9)
+#define UART_TX_EMPTY		BIT(8)
+#define UART_RX_OERR		BIT(1)
+#define UART_RX_DATA_AVAIL	BIT(0)
+
+struct pic32_uart_priv {
+	void __iomem *base;
+	ulong uartclk;
+};
+
+static void pic32_serial_setbrg(void __iomem *base, ulong uart_clk, u32 baud)
+{
+	writel(0, base + U_BRG);
+	writel((uart_clk / baud / 16) - 1, base + U_BRG);
+}
+
+/*
+ * Initialize the serial port with the given baudrate.
+ * The settings are always 8 data bits, no parity, 1 stop bit, no start bits.
+ */
+static int pic32_serial_init(void __iomem *base, ulong clk, u32 baudrate)
+{
+	/* wait for TX FIFO to empty */
+	wait_for_bit(__func__, base + U_STA, UART_TX_EMPTY,
+		     true, CONFIG_SYS_HZ, false);
+
+	/* send break */
+	writel(UART_TX_BRK, base + U_STASET);
+
+	/* disable and clear mode */
+	writel(0, base + U_MOD);
+	writel(0, base + U_STA);
+
+	/* set baud rate generator */
+	pic32_serial_setbrg(base, clk, baudrate);
+
+	/* enable the UART for TX and RX */
+	writel(UART_TX_ENABLE | UART_RX_ENABLE, base + U_STASET);
+
+	/* enable the UART */
+	writel(UART_ENABLE, base + U_MODSET);
+	return 0;
+}
+
+/* Output a single byte to the serial port */
+static void pic32_serial_putc(void __iomem *base, const char c)
+{
+	/* if \n, then add a \r */
+	if (c == '\n')
+		pic32_serial_putc(base, '\r');
+
+	/* Wait for Tx FIFO not full */
+	wait_for_bit(__func__, base + U_STA, UART_TX_FULL,
+		     false, CONFIG_SYS_HZ, false);
+
+	/* stuff the tx buffer with the character */
+	writel(c, base + U_TXR);
+}
+
+/* Check number of characters in RX fifo */
+static int pic32_serial_tstc(void __iomem *base)
+{
+	/* check if rx buffer overrun error has occurred */
+	if (readl(base + U_STA) & UART_RX_OERR) {
+		readl(base + U_RXR);
+
+		/* clear OERR to keep receiving */
+		writel(UART_RX_OERR, base + U_STACLR);
+	}
+
+	return readl(base + U_STA) & UART_RX_DATA_AVAIL;
+}
+
+/*
+ * Read a single byte from rx fifo.
+ * Blocking: waits until a character is received, then returns.
+ * Return the character read directly from the UART's receive register.
+ */
+static int pic32_serial_getc(void __iomem *base)
+{
+	/* return error until data is available */
+	if (!pic32_serial_tstc(base))
+		return -EAGAIN;
+
+	/* read the character from rx buffer */
+	return readl(base + U_RXR) & 0xff;
+}
+
+static int pic32_uart_pending(struct udevice *dev, bool input)
+{
+	struct pic32_uart_priv *priv = dev_get_platdata(dev);
+
+	if (input)
+		return pic32_serial_tstc(priv->base);
+
+	return !(readl(priv->base + U_STA) & UART_TX_EMPTY);
+}
+
+static int pic32_uart_setbrg(struct udevice *dev, int baudrate)
+{
+	struct pic32_uart_priv *priv = dev_get_platdata(dev);
+
+	pic32_serial_init(priv->base, priv->uartclk, baudrate);
+	return 0;
+}
+
+static int pic32_uart_putc(struct udevice *dev, const char ch)
+{
+	struct pic32_uart_priv *priv = dev_get_platdata(dev);
+
+	pic32_serial_putc(priv->base, ch);
+	return 0;
+}
+
+static int pic32_uart_getc(struct udevice *dev)
+{
+	struct pic32_uart_priv *priv = dev_get_platdata(dev);
+
+	return pic32_serial_getc(priv->base);
+}
+
+static int pic32_uart_probe(struct udevice *dev)
+{
+	struct pic32_uart_priv *priv = dev_get_platdata(dev);
+
+	pic32_serial_init(priv->base, priv->uartclk, CONFIG_BAUDRATE);
+	return 0;
+}
+
+static int pic32_uart_ofdata_to_platdata(struct udevice *dev)
+{
+	struct pic32_uart_priv *priv = dev_get_platdata(dev);
+	struct udevice *clkdev;
+	fdt_addr_t addr;
+	int ret;
+
+	/* get address */
+	addr = dev_get_addr(dev);
+	if (addr == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	priv->base = pic32_ioremap(addr);
+
+	/* get clock rate */
+	ret = uclass_get_device(UCLASS_CLK, 0, &clkdev);
+	if (ret) {
+		printf("clk class not found, %d\n", ret);
+		return ret;
+	}
+
+	priv->uartclk = clk_get_periph_rate(clkdev, PB2CLK);
+
+	return 0;
+}
+
+static const struct dm_serial_ops pic32_uart_ops = {
+	.putc		= pic32_uart_putc,
+	.pending	= pic32_uart_pending,
+	.getc		= pic32_uart_getc,
+	.setbrg		= pic32_uart_setbrg,
+};
+
+static const struct udevice_id pic32_uart_ids[] = {
+	{ .compatible = "microchip,pic32mzda-uart" },
+	{}
+};
+
+U_BOOT_DRIVER(pic32_serial) = {
+	.name		= "pic32-uart",
+	.id		= UCLASS_SERIAL,
+	.of_match	= pic32_uart_ids,
+	.probe		= pic32_uart_probe,
+	.ops		= &pic32_uart_ops,
+	.flags		= DM_FLAG_PRE_RELOC,
+	.ofdata_to_platdata = pic32_uart_ofdata_to_platdata,
+	.platdata_auto_alloc_size = sizeof(struct pic32_uart_priv),
+};
+
+#ifdef CONFIG_DEBUG_UART_PIC32
+#include <debug_uart.h>
+
+static inline void _debug_uart_init(void)
+{
+	void __iomem *base = (void __iomem *)CONFIG_DEBUG_UART_BASE;
+
+	pic32_serial_init(base, CONFIG_DEBUG_UART_CLOCK, CONFIG_BAUDRATE);
+}
+
+static inline void _debug_uart_putc(int ch)
+{
+	writel(ch, CONFIG_DEBUG_UART_BASE + U_TXR);
+}
+
+DEBUG_UART_FUNCS
+#endif
-- 
1.8.3.1